This invention relates generally to gas generation and, more particularly, to devices and methods for inflating an inflatable device such as an inflatable vehicle occupant restraint of a respective inflatable restraint system.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an xe2x80x9cairbag cushion,xe2x80x9d that is inflated or expanded with gas such as when the vehicle encounters sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins to be inflated, in a matter of no more than a few milliseconds, with gas produced or supplied by a device commonly referred to as an xe2x80x9cinflator.xe2x80x9d
Many types of inflator devices have been disclosed in the art for the inflating of one or more inflatable restraint system airbag cushions. Prior art inflator devices include compressed stored gas inflators, pyrotechnic inflators and hybrid inflators. Unfortunately, each of these types of inflator devices has been subject to certain disadvantages such as one or more of having a greater than desired weight, requiring more than desired space or volume, producing undesired or nonpreferred combustion products in greater than desired amounts, and producing or emitting gases at a greater than desired temperature, for example. Further, in those inflator devices that rely upon the reaction of a gas generant material or fuel to produce or provide inflation gas, the cost of producing or supplying such gas generant material or fuel and associated inflator device may be greater than would otherwise be desired.
Various relatively low cost materials are available which when contacted with water will liberate heat and form hydrogen-containing products, e.g., hydrogen and/or one or more various hydrocarbons. For example, hydrogen can rapidly be produced as one primary reaction product when a metal hydride, such as lithium hydride, is contacted with water.
Unfortunately, the greater or more extensive use of water-reactive materials in inflator technology has generally been limited as a result of various safety and manufacturing concerns. As will be appreciated, the reactivity of these materials when in contact with water has generally necessitated that such water-reactive materials be kept dry or free of contact with water during both the manufacturing process and while in the inflator in a static or nonactivated state. In practice this has generally necessitated that water-reactive materials be stored or held separately from contact with water, including the water charge such as needed for subsequent reaction upon actuation, both during manufacture and while in a subject inflator device in a static state or condition. As a result, the manufacturing and design costs associated with these materials, their use and corresponding or associated inflator devices that use or incorporate these materials have traditionally been relatively high and thus the use of such water-reactive materials has not been generally successfully pursued as a viable option as compared to inflator device use of pyrotechnic gas generant materials and the like, for example.
Thus, there remains a need and a demand for a gas generating device, an apparatus for inflating an inflatable device and a method for inflation that each more freely permits the use of lower cost reactant materials such as when contacted with water will liberate heat and form hydrogen-containing products, e.g., hydrogen and/or one or more various hydrocarbons, as described above. In particular, there exists a need and demand for an inflator device and inflation method that may desirably facilitate or otherwise more easily permit the advantageous use of such water-reactive compounds while avoiding or minimizing one or more of the shortcomings or limitations relating to the prior use of water-reactive compounds in such inflation applications.
There has been and continues to be significant interest in gas generant compositions incorporation and use of ammonium nitrate. In particular, ammonium nitrate is a relatively low cost, readily available and generally high gas yield component material for inclusion in such compositions.
Unfortunately, the general incorporation and use of ammonium nitrate in pyrotechnic gas generant formulations have generally been subject to certain difficulties. For example, ammonium nitrate-containing pyrotechnic gas generant formulations have commonly been subject to phase or other changes in crystalline structure such as may be associated with volumetric expansion such as may occur during temperature cycling over the normally expected or anticipated range of storage conditions, e.g., temperatures of about xe2x88x9240xc2x0 C. to about 110xc2x0 C. Such changes of form or structure may result in physical degradation of such gas generant formulation forms such as when such a gas generant formulation has been shaped or formed into tablets, wafers or other selected shape or form. Further, such changes, even when relatively minute, can strongly influence the physical properties of a corresponding gas generant material and, in turn, strongly affect the burn rate of the generant material. Unless checked, such changes in ammonium nitrate structure may result in such performance variations in the gas generant materials incorporating such ammonium nitrate as to render such gas generant materials unacceptable for typical inflatable restraint system applications.
In view of the above, there is a need and a demand for a gas generating device, an apparatus for inflating an inflatable device and a method for inflation that enhance the likelihood of greater or more widespread use of reactant materials such as ammonium nitrate.
A general object of the invention is to provide an improved gas generation or inflation device and method for inflating an inflatable safety device.
A more specific objective of the invention is to overcome one or more of the problems described above.
The general object of the invention can be attained, at least in part, through an improved gas generating device wherein a fuel material reacts to form gas generation reaction products. In accordance with one preferred embodiment of the invention, such a gas generating device includes a first chamber having contents including a quantity of a water-supplying compound and a quantity of a fuel precursor. The gas generating device also includes an initiator in discharge communication with at least a portion of the quantity of water-supplying compound content of the first chamber to form water. At least a portion of the formed water reacts with at least a portion of the quantity of fuel precursor to form a quantity of the fuel material and resulting in opening of the first chamber with a release of at least a portion of the fuel material therefrom.
The prior art has generally failed to provide an inflator device and inflation method that may desirably facilitate or otherwise more easily permit the advantageous use of compounds that react with water such as to form one or more hydrogen-containing materials such as hydrogen gas or a hydrocarbon while avoiding or minimizing one or more of the shortcomings or limitations relating to the prior use of water-reactive compounds in such inflation applications. The prior art also has generally failed to provide an inflator device and inflation method that may desirably facilitate or otherwise more easily permit the advantageous use of compounds such as ammonium nitrate without incurring undesired complications such as described above relating to form and structure on the ammonium nitrate and the resulting performance characteristics thereof.
The invention further comprehends, in accordance with another embodiment of the invention, an apparatus for inflating an inflatable device. The apparatus includes a closed first chamber having contents including a quantity of ammonium nitrate and a quantity of a fuel precursor, the fuel precursor being water reactive. The apparatus also includes an initiator in discharge communication with the contents of the first chamber for initiating decomposition of at least a portion of the quantity of ammonium nitrate to form water. Upon such initiation, at least a portion of the formed water reacts with at least a portion of the quantity of the fuel precursor to form a fuel material. The first chamber is adapted to open when a predetermined increase in pressure within the first chamber is realized whereby at least a portion of the fuel material is emitted from the first chamber.
The apparatus further includes a second chamber containing a quantity of pressurized stored gas including a quantity of oxidant material. The second chamber is in fluid communication with the first chamber upon the opening of the first chamber with at least a portion of the fuel material emitted from the first chamber reacting with at least a portion of the oxidant material to form inflation gas. The second chamber is adapted to open when a predetermined increase in pressure within the second chamber is realized whereby at least a portion of the product gas is emitted from the second chamber to inflate the inflatable device.
In accordance with yet another embodiment of the invention, an improvement in a vehicular inflatable safety assembly wherein a fuel material reacts to form gas generation reaction products. More specifically, the improvement relates to the assembly containing a quantity of a water-supplying compound and a quantity of a water-reactive fuel precursor effective upon initiation to form the fuel material in situ.
The invention also comprehends a method for inflating an inflatable safety device in a vehicle. In accordance with one embodiment of the invention, such method includes heating a mixture containing at least a water-supplying compound and a water-reactive fuel precursor to form a fuel material. The formed fuel material is subsequently contacted with a quantity of compressed gas, the compressed gas including a quantity of oxidant. At least a portion of the formed fuel material reacts with at least a portion of the quantity of the oxidant to produce heat. At least a portion of the produced heat is used to heat a stored quantity of inert gas to increase the volume of the inert gas with at least a portion of the increased volume of gas passed into the inflatable safety device to effect the inflation thereof.
The invention still further comprehends an improved method for inflating an inflatable safety device in a vehicle wherein a fuel material reacts to form gas generation reaction products. The improvement involves heating a mixture containing at least ammonium nitrate and a water-reactive fuel precursor to form the fuel material.
Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings.